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arXiv 1301.6763astro-ph.EP
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超级地球GJ1214b的斯皮策凌日及其大气意义

Spitzer Transits of the Super-Earth GJ1214b and Implications for Its Atmosphere

Jonathan D. Fraine, Drake Deming, Michaël Gillon, Emmanuël Jehin, Brice-Olivier Demory, Bjoern Benneke, Sara Seager, Nikole K. Lewis, Heather Knutson, Jean-Michel Desert

摘要:

2011年5月,我们使用4.5微米波长的温暖斯皮策在20天的准连续序列中观察到凌日的超地球系外行星GJ 1214 b。我们长期观测的目标是准确确定这颗附近超级地球的红外凌日半径,寻找二次日食,并在GJ 1214的宜居带寻找其他凌日行星。我们在这里报告GJ 1214 b过境监测的结果,包括对Desert等人(2011)先前过境观测的重新分析。总的来说,我们分析了GJ 1214 b在4.5微米处的14次凌日,在3.6微米处的3次凌日,以及在I+z波段的7次新的地基凌日。我们的新斯皮策数据本身消除了GJ 1214 b的无云太阳成分大气,以及Howe & Burrows(2012)的富甲烷模型。使用我们新的斯皮策测量来锚定GJ 1214 b在长波长处的观测到的过境半径,并在I+z中添加新的测量值,我们使用卡方分析来评估Benneke & Seager(2012)和Howe & Burrows(2012)的模型。我们发现,最佳拟合模型表现出增加在短波长的过境半径由于瑞利散射。纯水气氛也是可能的。然而,平坦线(未检测到大气)仍然是统计上可接受的最佳模型之一,并且优于纯水大气。我们探讨了来自不同观测组的结果之间的系统差异的影响,我们发现,即使考虑到观测者之间的系统差异,Howe & Burrows(2012)tholin-haze模型仍然是最佳拟合。

英文摘要:

We observed the transiting super-Earth exoplanet GJ1214b using Warm Spitzer at 4.5 microns wavelength during a 20-day quasi-continuous sequence in May 2011. The goals of our long observation were to accurately define the infrared transit radius of this nearby super-Earth, to search for the secondary eclipse, and to search for other transiting planets in the habitable zone of GJ1214. We here report results from the transit monitoring of GJ1214b, including a re-analysis of previous transit observations by Desert et al. (2011). In total, we analyse 14 transits of GJ1214b at 4.5 microns, 3 transits at 3.6 microns, and 7 new ground-based transits in the I+z band. Our new Spitzer data by themselves eliminate cloudless solar composition atmospheres for GJ1214b, and methane-rich models from Howe & Burrows (2012). Using our new Spitzer measurements to anchor the observed transit radii of GJ1214b at long wavelengths, and adding new measurements in I+z, we evaluate models from Benneke & Seager (2012) and Howe & Burrows (2012) using a chi-squared analysis. We find that the best-fit model exhibits an increase in transit radius at short wavelengths due to Rayleigh scattering. Pure water atmospheres are also possible. However, a flat line (no atmosphere detected) remains among the best of the statistically acceptable models, and better than pure water atmospheres. We explore the effect of systematic differences among results from different observational groups, and we find that the Howe & Burrows (2012) tholin-haze model remains the best fit, even when systematic differences among observers are considered.

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